1. Field
The present disclosure generally relates to switches, and more particularly to switches having extended termination bandwidth.
2. Description of the Related Art
Absorptive switches are used in some radio-frequency (RF) applications, where it is desirable to have switches that have a selected impedance presented to the switch's input and/or output when the switch is in its OFF state. Such an OFF-state impedance may or may not be substantially the same as that of the switch's ON state. For the purpose of description herein, it will be assumed that when a switch is in its ON state, RF signal is allowed to pass between the switch's input and output. Meanwhile, when in its OFF state, RF signal is not allowed to pass between the input and the output.
For RF switches intended to be used over relatively large bandwidths, achieving well-controlled termination impedance across a specified frequency range can be challenging. Such a challenge can be due to, for example, on-chip DC blocking capacitors typically used in the switch termination leg resonating with inductance provided by a chip bond wire. Such bond wires and/or capacitors can be configured for specific operating frequencies, but the associated bandwidth is often not sufficient to provide desirable termination impedance across all of the specific operating frequencies. In some situations, parasitic capacitances of switch devices can also be a factor in the termination impedance, particularly at high frequencies. The effects of the parasitics can be managed by, for example, resizing the devices. However, such a measure can lead to degradation in other performance metrics such as insertion loss and isolation.